The present invention relates generally to appliance control mechanisms, and more particularly to damper drive mechanisms and timer/sequence switch control mechanisms used for appliances.
Consumer and commercial appliances, such as dishwashers, washing machines, dryers, etc., typically operate under control of a sequenced program that controls the duration and number of cycles through which the appliance runs to accomplish the selected program. Heretofore, electromechanical program timers have been employed for such appliances wherein a rotary cam is periodically advanced or indexed by a timed advance mechanism for affecting sequential actuation and deactuation of a plurality of machine or appliance function control switches. In such typical known electromechanical program timer arrangements, one full revolution of the cam comprises a complete program interval or cycle for the machine or appliance.
Because the timing accuracy and number of switch actuations and deactuations controllable in a given program interval is limited by the available circumference of the cam, which in turn is limited by the size or volume of the program timer, many modern appliances have replaced the electromechanical program timer with a switch sequence controller. These more modern switch sequence controllers utilize programmable electronics to drive a motorized advance connected to a cam to position the switch cam to a desired position at a desired time rather than to continuously advance or periodically index a program cam through a revolution of rotary movement for the program cycle. These more modern hybrid programmers use electronics to control the cam advance motor for intermittent operation to achieve the desired sequence of switch operation instead of progressively advancing a program cam at a fixed rate and relying on the program cam profile to achieve the desired sequencing of the function control switches. As a result, the hybrid programmer provides the sophistication of electronic program control, yet retains the robustness of mechanically actuated electrical switching contacts which is required for switching relatively high current loads repeatedly over prolonged service. One such sequencing switch for use in a hybrid programmer is described in U.S. Pat. No. 5,828,019, entitled Motorized Sequencing Switch Assembly, issued Oct. 27, 1998, and assigned to the Assignee of the present application the teachings and disclosure of which are hereby incorporated in their entireties by reference thereto.
As one of the components typically controlled by the program sequencing operation of the typical electromechanical program timer or the more modern hybrid programmer, many appliances include at least one vent with a controlled damper to open and close the vent. For example, modern dishwashers typically include a damper controlled vent that is opened during a drying cycle to vent the cleaning tub area, and that is closed during the washing cycle to preserve the energy within the tub and to reduce the amount of noise that escapes therefrom. In conventional appliance design, these damper controlled vents comprise a drive motor coupled to the damper through a worm gear. When the program timer or hybrid programmer determines that it is time to open the damper on the vent, an electrical contact to the motor is closed which energizes the motor and begins rotation of the worm gear in a direction to open the vent. When the program timer or hybrid programmer determines that it is time to close the vent, an electrical contact is closed to energize the motor to rotate the worm gear in the opposite direction to close the damper on the vent. While this configuration performs well, the increased cost and energy usage of the damper drive motor is undesirable. There exists, therefore, a desire in the art to reduce the cost and energy consumption necessitated by controlled damper operation in consumer and commercial appliances and other machines.
In view of the above, it is an object of the present invention to provide a new and improved rotary drive mechanism, timer sequence switch, and appliance that overcomes the above identified and other problems existing in the art.
In one embodiment of the present invention, a rotary drive mechanism operative in association with a rotary cam having a control track is presented. The rotary drive mechanism translates linear motion of the control track to rotary motion. This rotary drive mechanism comprises a housing, and a tracking rod rotatably secured within the housing. The tracking rod has a tracking lobe adapted to engage the control track of the rotary cam, and a tracking gear. The mechanism also includes an actuating rod rotatably secured within the housing and a driving end extending through the housing. This actuating rod also includes an actuating gear positioned to drivably engage the tracking gear. Rotation of the tracking rod though a first angle causes rotation of the actuating rod though a second angle determined by a gear ratio between the tracking gear and the actuating gear. Preferably, the gear ratio is approximately 2:1 resulting in an approximately 180xc2x0 rotation of the actuating rod upon an approximately 90xc2x0 rotation of the tracking rod. In one embodiment, the mechanism further comprises a torsion spring drivably coupled to the actuating rod external to the housing.
In a preferred embodiment, the tracking rod further includes a bias lobe oriented in an angular relationship to the tracking lobe. In this embodiment, the mechanism further comprises a bias spring affixed in the housing, and imparting a bias force on the bias lobe. This force positions the tracking lobe in a quiescent position absent interference from the control track. Preferably, the bias spring comprises a leaf spring having a first end affixed to the housing and a second end extending toward the bias lobe. This leaf spring defines a contact slide surface from the first end to the second end. The bias lobe slides along this contact slide surface under the bias force to return the tracking lobe to the quiescent position absent interference from the control track. In a further preferred embodiment, the tracking gear comprises an arc segment gear traversing approximately 90xc2x0 and having a first and a second radial side. The housing also includes a tracking gear stop positioned to contact the first radial side when the tracking lobe is in the quiescent position. Preferably, the actuating gear includes a first and a second locating lobe extending radially from the actuating gear. In one embodiment, the second locating lobe contacts the second radial side in the quiescent position, and the first locating lobe contacts the first radial side when the tracking gear is rotated to an activated position.
In an alternate embodiment of the present invention, a rotary drive mechanism adapted to translate linear rise and fall motion of a cam control track to rotary motion comprises a housing, a tracking rod rotatably fixed in the housing, and means for tracking the cam control track. This tracking means imparts rotary motion to the tracking rod in response to the linear rise and fall of the cam control track. The mechanism also includes an actuating rod rotatably fixed in the housing having an end extending though the housing, and rotary motion multiplying means operatively attached to the tracking rod and to the actuating rod. This means transmits rotary motion from the tracking rod to the actuating rod. The rotary motion imparted to the actuating rod is a multiple of the rotary motion of the tracking rod.
In one embodiment, the tracking means comprises a tracking lobe extending from the tracking rod. Preferably, the tracking means further comprises a bias lobe extending from the tracking rod in an angular relationship to the tracking lobe, and a bias spring imparting a bias force on the bias lobe. This bias force acts in opposition to a force applied to the tracking lobe by the rise in the cam control track, which enables the tracking lobe to track the falls in the cam control track. Alternatively, the tracking means comprises a torque arm extending from the tracking rod, and a tracker linearly movable within the housing and in communication with the torque arm. Linear movement of the tracker imparts rotary motion to the tracking rod though the torque arm. Preferably, the tracking means further comprises a bias spring imparting a bias force on the torque arm acting in opposition to a force applied to the torque arm by the tracker, which enables the tracker to track the falls in the cam control track.
In a preferred embodiment, the rotary motion multiplying means comprises a tracking gear operatively attached to the tracking rod, and an actuating gear operatively attached to the actuating rod. This actuating gear is positioned to drivably engage the tracking gear. The multiple of the rotary motion of the tracking rod imparted to the actuating rod is determined by a gear ration between the actuating gear and the tracking gear. Preferably, the tracking gear comprises an arc segment gear traversing approximately 90xc2x0 and having a first and a second radial side. The actuating gear includes a first and a second locating lobe extending radially from the gear. The second locating lobe contacts the second radial side when the means for tracking the cam control track is tracking a fall in the cam control track. The first locating lobe contacts the first radial side when the means for tracking the cam control track is tracking a rise in the cam control track.
In a further alternate embodiment, an appliance timer/sequence switch providing a program-controlled rotary output is presented. This timer/sequence switch comprises a motor having an output shaft, a cam drivably coupled to the output shaft and having at least one cam control track on its surface, and a rotary drive mechanism. This rotary drive mechanism has a cam control track follower adapted to linearly follow the cam control track, and an output actuating rod providing rotary motion corresponding to linear deviations of the cam control track. The rotary drive mechanism further comprises a tracking rod drivably coupled to the cam control track follower. This tracking rod is rotated by the cam control track follower during the linear deviations of the cam control track. The tracking rod rotatably drives the actuating rod though a gear set having an input to output ratio multiplying rotary motion of the tracking rod to the actuating rod.
In one embodiment of the timer/sequence switch, the cam control track follower comprises a tracking lobe extending from the tracking rod, a bias lobe extending from the tracking rod in an angular relationship to the tracking lobe, and a bias spring imparting a bias force on the bias lobe to maintain the cam control track follower in contact with the cam control track. In an alternate embodiment, the cam control track follower comprises a torque arm extending from the tracking rod, and a tracker linearly movable within the rotary drive mechanism and in communication with the torque arm. Linear movement of the tracker imparts rotary motion to the tracking rod though the torque arm. The cam control track follower further comprises a bias spring imparting a bias force on the torque arm acting in opposition to a force applied to the torque arm by the tracker. This enables the tracker to maintain contact with the cam control track.
A further embodiment of the present invention presents an appliance comprising a vent having a damper rotatable between an opened and a closed position, and a program timer operative to control operating cycles of the appliance. This program timer includes a motor driven cam having a vent control track on its surface. The appliance also includes a rotary drive mechanism having a vent control track follower adapted to follow the vent control track. The rotary drive mechanism further includes an output actuating rod providing rotary motion corresponding to vent control track. A torsional actuator is drivably coupled between the output actuating rod and the damper. Preferably, the torsional actuator comprises a torsion spring.
In one embodiment of the appliance, the rotary drive mechanism further comprises a tracking rod drivably coupled to the vent control track follower. This tracking rod is rotated by the vent control track follower during linear deviations of the vent control track, and rotatably drives the output actuating rod though a gear assembly. The gear assembly has a gear ratio though which rotary motion of the tracking rod is multiplied to the actuating rod. Preferably, the vent control track follower comprises a tracking lobe extending from the tracking rod, a bias lobe extending from the tracking rod in an angular relationship to the tracking lobe, and a bias spring imparting a bias force on the bias lobe to maintain the vent control track follower in contact with the vent control track. Alternatively, the vent control track follower comprises a torque arm extending from the tracking rod, and a tracker linearly movable within the rotary drive mechanism and in communication with the torque arm. In this embodiment, linear movement of the tracker imparts rotary motion to the tracking rod though the torque arm. The vent control track follower further comprises a bias spring imparting a bias force on the torque arm acting in opposition to a force applied to the torque arm by the tracker thereby enabling the tracker to maintain contact with the cam control track.
Other objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.